The ferrite core does not eliminate EFI/RFI ...its job is to arrest EFI/RFI before it reaches the head unit ...

If the ferrite core is put anywhere in the cable except right before the head unit ... Other stray EFI/RFI can get in the cable between the ferrite core and the head unit and show in the unit display as interference ...

Install the ferrite core as close to the head unit as possible ...



Rickie